Low concentration CO2 capture performance of Li4SiO4 adsorbent: Effect of alkali metals (Na and K) and alkaline earth metals (Mg and Ca) doping

Abstract

Li 4 SiO 4 is a promising CO 2 capture material with significant commercial potential. However, its capture efficiency significantly decreases at lower CO 2 concentrations typically encountered in industrial flue gases (below 15 ​vol%). Therefore, enhancing the adsorption performance of Li 4 SiO 4 under low CO 2 partial pressures through doping modification is critical for practical applications. This study systematically investigates the impact of alkali metal (K and Na) and alkaline earth metal (Mg and Ca) doping on the CO 2 capture performance of Li 4 SiO 4 . The results showed that doping significantly improved the adsorption capacity and cyclic stability of Li 4 SiO 4 under low CO 2 concentrations. Specifically, at a CO 2 concentration of 5 ​vol%, pure Li 4 SiO 4 exhibits a dynamic equilibrium capture capacity of 5.70 ​wt%, whereas the doped samples—Li 4 SiO 4 –15Na, Li 4 SiO 4 –15K, Li 4 SiO 4 –15Mg, and Li 4 SiO 4 –25Ca—achieve significantly enhanced capacities of 19.73 ​wt%,15.41 ​wt%, 11.62 ​wt%, and 13.19 ​wt%, respectively. Although Mg-doped and Ca-doped samples demonstrate relatively poor stability during multiple desorption cycles, samples doped with Na and K exhibit excellent cycling durability. These findings provide valuable insights for optimizing Li 4 SiO 4 -based adsorbents and support their practical application in industrial carbon capture processes. • Na,K,Mg,Ca doping boosts Li 4 SiO 4 ​CO 2 ​uptake and cyclic stability at low concentrations. • Na/K-doped Li 4 SiO 4 ​shows top low-CO 2 ​stability with minimal degradation. • Na/K-Li 4 SiO 4 ​excels in low-CO 2 ​capture aiding practical industrial use.